Spid Rear End Question
 

Here are 2 spid labels. The blue one is from a 71 GMC Burb and the green one is from a 72 Chev Burb. Now I think the 350 engine codes are for the same engine. I always thought the small block burbs came stock with 3:73 rear ends and the big blocks came with 3:08 rears stock. If that is the case why would the one spid show the 3:73 axle and the other not ? The main reason the guy is selling the green one ( with the 3:73's ) is because he says he cant afford to drive it. I guess my question is why is the 3:73 axle printed out on one spid and not the other ?

Re: Spid Rear End Question
 

Greg...I'm gonna move this to the main board where it'll get more action:D

Re: Spid Rear End Question
 

small block with an auto or 4 speed got 3.07 gears. 3.73 was if it was a manual 3 speed. So the 3.73 is listed becouse it was not base equipment with that engine/tranny combo.

Re: Spid Rear End Question
 

Thank You LM

Re: Spid Rear End Question
 

correction... not small block... 350. 307 engines commonly came with the 3.73 gear.

Re: Spid Rear End Question
 

That makes sense as the 307 wouldn't be as powerful as the 350 so the lower (3:73) gears would help the driveability of the heavy Burb with a 307.

Re: Spid Rear End Question
 

My '70 2WD Burb came with a 307 and truck 4 speed. It has the 3.07 rear gear and it isn't listed as an option on the SPID.

Re: Spid Rear End Question
 

Thinking out loud about this a 307 with the garnny 4 speed should have reasonably good pulling power but the 3 speed autos would be a little sluggish with the 3:07 gears.

Re: Spid Rear End Question
 

I don't know what the ratio for a 3 spd first gear is as compared to the second gear on the 4 speed, but I do know that I never had to use the granny gear to start out when I had the original 4 speed in it. I always used 2nd which is actually felt like a regular first gear.

Re: Spid Rear End Question
 

I believe the reason that Suburban was ordered with 3.73s is because it also had the optional L78 rubber.

Re: Spid Rear End Question
 

While we're on the subject. What would be the typical gearing on a big block 1/2 ton?

Re: Spid Rear End Question
 

3.07 unless optioned otherwise

Re: Spid Rear End Question
 

While we're still on the subject what about a C20 big block?

Re: Spid Rear End Question
 

C/20 came with the dana rear and 3.54 gearing... again, unless optioned otherwise.